This invention relates to a tool monitor and assembly qualifier that verifies that the correct number of fasteners have been properly installed into an assembly. When used in conjunction with a pneumatic pulse tool, pneumatic tool, electric tool, or mechanical click wrench containing a mechanical clutch or torque switch, proper fastener installation and count can be verified. The device monitors an analog signature created by a tools internal pressure, current flow or voltage and has the ability to xe2x80x9clearnxe2x80x9d the analog curve""s characteristics during the assembly process.
U.S. Pat. Nos. 6,055,484 and 5,937,370 represent a recent, significant development in the field of tool monitoring and assembly qualifying. The programmed microprocessor is configured to identify a portion of the signal representative of the analog signal corresponding to a completed cycle. The configuration also allows for identification of an incomplete cycle and a multiple counting of a completed cycle (double-hit). A completed cycle occurs when a tool drives a fastener to completion causing the tool""s mechanical clutch or torque switch to end the cycle. An incomplete cycle occurs when a tool drives a fastener and the clutch or torque switch is not allowed to complete the cycle by turning the tool off, meaning that the proper torque is never reached. A double-hit occurs when a tool drives a fastener that has previously been tightened to the target torque. The qualifiers and disclosures of U.S. Pat. Nos. 6,055,484 and 5,937,370 are herein incorporated by reference.
In the previous invention, the programmed microprocessor is configured to identify and store the parameter of a first period of time for the analog signal to attain an initial predetermined range. The microprocessor also is configured to identify and store the parameter of a first period of time for the analog signal to attain an initial predetermined range. The microprocessor also is configured to identify and store a second period of time for the analog signal to attain a second predetermined range. The qualifier quite nicely tells if a fastener is put in properly and if the clutch or torque switch has fired indicating that a fastening process is complete.
The next generation qualifier uses multiple thresholds and multiple timers to perform its operations. This assembly qualifier is a counting apparatus that monitors either the pressure of a pneumatic tool, the current flow through an electric tool, or the switch closure of a torque switch on a mechanical wrench to determine if the tool""s clutch has shut the tool off indirectly confirming that the target torque has been reached. The qualifier also determines if some unknown means shut off the tool besides the clutch. For example, the system detects proper fastening, nuisance trips, double hits, fasteners that are too short, fasteners that are too long, the use or nonuse of washers, effective or non-effective pulsing, and proper clutch shut off. The microprocessor may also be configured to identify and store a third period of time for the analog signal to attain a third predetermined range. This version makes use of up to four thresholds and five timers in order to accomplish its qualification of an assembly process.
This system for monitoring analog signatures comprised of a means to convert air pressure, electrical current, or a switch closure into an electrical signal representative of the aforementioned pressure, current, or switch closure, a means for electrically computationally processing the electrical signal into another signal representing at least one parameter corresponding to a condition of the tool being monitored which is a function of the analog signal, and a programmed microprocessor configured to identify a portion of the analog signal corresponding to the parameter. The programmed microprocessor is configured to identify and store the parameter of a first threshold analog signal to begin monitoring and storing the parameter of a cycle. Next, the programmed microprocessor is configured to identify and store the parameter of a second analog level of the tool driving the fastener to its target torque and configured to identify and store the parameter of a third analog level to count a completed cycle when the measured analog signal is in the same as the third identified and stored parameter. Finally, the programmed microprocessor is configured to identify and store the parameter of a fourth analog level which indicates the shut off region of the cycle when the measured analog signal is above the fourth identified and stored parameter.
Certain pulse pneumatic have an internal mechanical device that regulates (governs) the incoming air supply. Because of this, the pneumatic signature can xe2x80x9cfoolxe2x80x9d the qualifier by creating a signal that would satisfy all of the timers and thresholds even though the tool was in reverse or running in the air and not tightening a fastener at all.
With these particular pneumatic tools the difference between a xe2x80x9cgoodxe2x80x9d run-down and the other anomalies were the pulses. Even though the other qualification methods were used to insure that the pressure was in a window where it was considered to be pulsing, that logic was not sufficient in this case.
This invention is a pulse counting algorithm that knows how to identify individual pulses. When the unit is in cycle and collecting data, the algorithm determines if the current data point being sampled is in the region (between the thresholds) where pulsing is expected to occur. If it is, a pulse width worth of samples leading up to the point are retrieved from memory. A variable referred to as a DELTA represents the minimum peak to valley differential the algorithm is willing to accept as a pulse. The algorithm analyzes the data point that would be the center of the data that has been pulled from memory. The algorithm looks to see if there are data points that are the value DELTA less than the point that is being analyzed on both sides of the data point within the pulse width worth of data that is being analyzed. If there are, this point is considered to be a positive pulse.
A count of all the positive pulses is kept during a rundown and this pulse count is compared to the desired number of pulses at the end of the run.
At the end of the run, if all criteria are met including timers, thresholds, and number of pulses, then the fastening is considered good.